The present invention relates to a fluid pressure modulation valve having particular application as a part of an anti-lock, anti-skid maximum effective braking force, hydraulic brake system. The invention, more particularly, relates to a modulator adapted for installation fluidly intermediate between an automobile's master cylinder and a vehicle wheel brake actuator to achieve linear control of brake pressure to the wheels of the automobile that is responsive to selective sensed wheel conditions.
It has been previously recognized in the prior art that the application of a braking force for the slowing of rotation of a rotating wheel is subject to a phenomenon known as wheel locking. In the automotive context, such locking will occur when the rolling friction between the wheel and the road surface is overcome and, thereupon slipping of the auto wheel relative to the road surface occurs. The dangers inherent in such locking are well known, and includes the loss of steering control, skidding, reduced effective braking force and loss of directional stability of the vehicle.
Approaches intended to deal with the above problem have appeared in the prior art and, as best known to the inventor, are represented by U.S. Pat. Nos. 3,837,711 (1974) to Van House et al, entitled Anti-Brake Pressure Modulator; No. 3,880,476 (1975) to Belart et al, entitled Electromagnetic Valve; No. 4,068,904 (1978) to Blomberg et al, entitled Anti-locking Brake Apparatus and Method; and No. 4,070,069 (1978) to Belart et al, entitled Brake Control Arrangement For Hydraulic Brake Control Systems.
None of the prior art known to the inventor, with the exception of Van House above, makes use of the selective positioning of a piston/piston rod within a hydraulic cylinder to alter the available force outputted from the master cylinder and applied to the brake.
The present invention is accordingly a direct improvement of Van House in that the structure and method of the inventor set forth below defines a suitable modulation and force output control achievable with the use of a smaller reciprocating input force and in addition the instant invention is more adaptable to construction in smaller dimensions, as is necessary to effectively apply the principles embodied in the subject invention to a practical anti-locking brake system.